1. Field of the Invention
The present invention relates to a composite bearing member used for a rotary electrical machine or the like, a manufacturing method of a composite bearing member, a bearing device having this composite bearing member, and a rotary electrical machine having this bearing device.
2. Description of the Related Art
Recently, as industrial technology develops, various kinds of bearings are required to cope with speed-up of a rotary shaft, to have a high surface pressure, and so on. Conventionally, a white metal (for example, type I: Sn 88 to 92 wt %, Sb 5 to 7 wt %, Cu 3 to 5 wt %) has been often used as a bearing material. However, since such a soft metal material has a low fusing point, and has problems of significant deterioration of a strength at a high temperature and of burning, so that its range of use is limited.
A polytetrafluoroethylene (PTFE) resin material has a low friction coefficient and a superior heat resistance, and is suitable as a bearing material. Further, a polyether ether ketone (PEEK) resin material and a polyimide (PI) resin material each have a slightly higher friction coefficient compared with the polytetrafluoroethylene resin material, but is superior in a mechanical property at a high temperature. By addition of various kinds of ceramics fibers or particle filler to the above-described resin materials, a sliding material having both the mechanical property, a friction characteristic and an abrasion characteristic can be produced.
In order to obtain a bearing device whose bearing sliding surface is constituted with the above-described resin material and whose bearing base material is constituted with a metal material, it is necessary to join the resin material and the metal material being heterogeneous materials in a manner to have a sufficient joining strength.
However, in a case that the resin material and the metal material are joined, if a joining method applied to joining of metal materials is adopted, it is difficult to obtain a sufficient joining strength. In other words, in a case that different metal members are joined by a molten metal solidification method, a diffusion reaction or the like is generated since both materials are metals, so that physical joining or chemical joining occurs in addition to mechanical joining. In contrast, in the case that the resin material and the metal material are joined, joining is simple mechanical joining, so that it is difficult to obtain a sufficient joining strength. Further, in a case that the resin material and the metal material are joined under a condition of a high temperature and a high pressure, deterioration of the resin material occurs, or a problem such as a manufacturing cost increase due to long time holding under the condition of the high temperature and the high pressure occurs.
Further, when the resin material and the metal material are to be joined, joining by using an adhesive agent or the like can be considered, but it is difficult to select an adhesive agent having good adhesiveness to both the resin material and the metal material. Further, in a case of a resin-based adhesive agent, since a joining interface between the resin and the metal necessarily exists, a bonding strength between the metal material and the resin material cannot be improved basically.
Further, when two kinds of members are to be joined, as a method to improve an interface strength, there is known a method of increasing a joining area by enlarging a surface area by means of honing, chemical etching or the like, for example. However, enlargement of the joining area by honing, chemical etching or the like is limited and a resistance against shear peeling of the interface is small, and therefore, a joining strength between heterogeneous materials cannot be increased sufficiently.
On the other hand, in consideration of various problems in a conventional bearing material, in JP-B2 3194866 (Patent Registration), for example, technology is suggested in which for joining a resin material and a metal material, a porous intermediate layer is provided on a surface of the metal material, and the resin material is stacked on the metal material while being filled into the porous intermediate layer. According to this invention, the porous intermediate layer is joined to a bearing base material under vacuum in advance.
When a bearing for a hydroelectric generator, for example, is created by using the above-described conventional method of joining the resin material and the metal material, a process for joining under vacuum is extremely expensive since a total weight of a bearing base material is from several hundred kilograms to several tons, and a manufacturing cost is increased. In addition, capacity of a vacuum facility is limited, creation under vacuum may be sometimes difficult.
Under the circumstances, in a bearing material made by joining heterogeneous materials such as a resin material and a metal material, for example, it is considered to be a problem to reduce a manufacturing cost without sacrificing performance or reliability of a bearing and without depending on facility capacity.